* Winx now returns io::Error
This commit is a spiritual follower of #1242 in the sense that it
adjusts `winx` to also return `io::Error` directly rather than
tossing a custom error type here and there.
* Adapt wasi-common to changes in winx
* Run cargo fmt
* Swap overly big map_err with explicit match
This commit fully implements `__wasi_fd_fdstat_get` on Windows so that
the descriptor flags can be determined.
It does this by calling into `NtQueryInformationFile` (safe to call from
user mode) to get the open mode and access of the underlying OS handle.
`NtQueryInformationFile` isn't included in the `winapi` crate, so it is
manually being linked against.
This commit also fixes several bugs on Windows:
* Ignore `__WASI_FDFLAG_NONBLOCK` by not setting `FILE_FLAG_OVERLAPPED`
on file handles (the POSIX behavior for `O_NONBLOCK` on files).
* Use `FILE_FLAG_WRITE_THROUGH` for the `__WASI_FDFLAG_?SYNC` flags.
* `__WASI_FDFLAG_APPEND` should disallow `FILE_WRITE_DATA` access to
force append-only on write operations.
* Use `GENERIC_READ` and `GENERIC_WRITE` access flags. The
latter is required when opening a file for truncation.
